Photo-Elastic Determination of Shrinkage Stresses

Abstract

Stresses due to shrinkage of concrete in masonry dams are of interest and importance, but the determination of these stresses is complex and difficult. In practice, the large masses of concrete used in gravity dams are not homogeneous; nor are they isotropic, as the structure is poured in blocks which present many planes of discontinuity. The indeterminate factors on these planes of discontinuity present such formidable difficulties that an accurate determination of shrinkage stresses is impossible. If the problem is idealized, however, by assuming a homogenous , isotropic, simple gravity dam subject to uniform shrinkage, it becomes possible to predict these stresses with some assurance. Although this idealized case is not truly consistent with actual practice, it creates a philosophical “picture,” nevertheless, of the strained condition that should be of value to the judgment of the de signing engineer.